A tool to convert MCNP geometries into the TRIPOLI-4® format
Project description
t4_geom_convert
This repository contains the development version of t4_geom_convert
, a Python
tool to convert MCNP geometries into the TRIPOLI-4® format.
Features
Here is a list of features of the MCNP modelling engine that are
at least partially supported and converted by t4_geom_convert
:
- All surface types (except SQ)
- Boolean cell operators
- Affine transformations on surfaces and on cells (see the Current limitations section though)
- Boundary conditions (reflection, white surfaces)
- Isotopic compositions and cell densities
- Universes and fills, even nested, possibly with affine transformations
- Lattices (see the Current limitations section though)
Installation
If you want to install the latest stable version, just type the following command in a terminal:
$ pip3 install t4_geom_convert
You can also install the latest development version with
$ pip3 install git+https://github.com/arekfu/t4_geom_convert.git@next
You might want to pass the --user
option to pip3
for a local install. Even
better, you can create a virtual environment and install t4_geom_convert
there with
$ python3 -m venv /path/to/some/folder
$ source /path/to/some/folder/bin/activate
$ pip3 install -U pip setuptools
$ pip3 install t4_geom_convert
Dependencies
The MCNP input file is parsed by MIP. We use a slightly modified version of
MIP, which is shipped along with t4_geom_convert
. MIP depends on TatSu
4.3.0.
t4_geom_convert
also depends on numpy
.
Usage
The basic usage is simply
$ t4_geom_convert <mcnp_input>
This will create a TRIPOLI-4 output file called <mcnp_input>.t4
containing
the converted geometry. You can also choose a different name for the output
file using the -o
option.
Use the -h
option for a list of all available options.
Lattice conversion
t4_geom_convert
is capable of handling the conversion of repeated structures
(lattices). Only hexaedral lattices (LAT=1
) are supported for the moment.
A hexaedral cell declared as LAT=1
represents the unit cell of the lattice,
which is assumed to repeat in all directions up to the boundaries of the
enclosing cell. Due to limitations of the TRIPOLI-4 representation of lattices,
we have chosen to represent lattices using a purely surface-based approach.
This means that t4_geom_convert
will actually emit separate cell definitions
for each cell of the lattice that is visible through the enclosing cell. The
ranges of cell definitions to be emitted must be specified by the user via the
--lattice
command-line option. For instance, consider the following MCNP
input:
A lattice example
1 0 -2 1 -4 3 IMP:N=1 U=2 LAT=1
10 1 -1. -10 IMP:N=1 FILL=2
1000 0 10 IMP:N=0
1 PX -1.5
2 PX 1.5
3 PY -0.5
4 PY 0.5
10 SO 4
m1 13027 1.
Here the unit cell is two-dimensional. The lattice fills a sphere of radius 4. Assuming the unit cell is indexed as (0,0), the visible lattice cells are
- (-1, -4) to (-1, 4)
- (0, -4) to (0, 4)
- (1, -4) to (1, 4)
This can be confirmed by visual inspection of the MCNP geometry or by
geometrical considerations. Once the index bounds are determined, the
--lattice
option must be specified as
$ t4_geom_convert --lattice 1,-1:1,-4:4 <mcnp_input>
↑ ↑ ↑ ↑ ↑
cell number ───┘ │ │ │ └ j-range upper bound
i-range lower bound ───┘ │ └─── j-range lower bound
i-range upper bound ───┘
This results in the following TRIPOLI-4 geometry (X-Y cut), where a few cell indices have been annotated:
The syntax for one-dimensional lattices is
--lattice <cell>,<i-from>:<i-to>
and for three-dimensional lattices it is
--lattice <cell>,<i-from>:<i-to>,<j-from>:<j-to>,<k-from>:<k-to>
Note that the ijk
axes are not necessarily the same as the coordinate axes.
The orientation of the lattice axes is specified by MCNP (see the Lattice
indexing paragraph in the User's Manual) and it is determined by the order in
which the surfaces of the unit cell appear specified. In our example, the first
surface appearing in the definition of the unit cell is surface 2
; therefore,
surface 2
separates the unit cell (0, 0) from cell (1, 0); the next surface
(1
) separates the unit cell from cell (-1, 0); the following surfaces, 4
and 3
, separate the unit cell from cells (0, 1) and (0, -1), respectively.
A lattice unit cell may appear as a fill pattern in several enclosing cells. It is currently not possible to specify different fill ranges for each of them.
Fully-specified lattices
MCNP provides a syntax for the specification of lattice with heterogeneous cells. An example is
A lattice example
c cells
2 0 -21 u=2 imp:n=1
21 0 21 u=2 imp:n=1
3 0 -31 u=3 imp:n=1
31 0 31 u=3 imp:n=1
10 0 -2 1 3 -4 lat=1 u=20 IMP:N=1
FILL=-1:1 -4:4
c i=-1 i=0 i=1
2 3 2 $ j=-4
2 3 2 $ j=-3
2 3 2 $ j=-2
2 3 2 $ j=-1
2 3 2 $ j=0
3 3 2 $ j=1
3 3 2 $ j=2
3 3 2 $ j=3
3 3 2 $ j=4
100 1 -1. -10 IMP:N=1 FILL=20
1000 0 10 IMP:N=0
1 PX -1.5
2 PX 1.5
3 PY -0.5
4 PY 0.5
10 SO 4
21 SO 0.4
31 SO 0.1
m1 13027 1.
The FILL=-1:1 -4:4
option indicates the range of indices where cells will be
specified. The universes filling the cells are detailed in the table below,
which by convention loops over the leftmost (i
) axis first. This syntax is
supported by t4_geom_convert
and does not require a --lattice
option. One
restriction applies: none of the subcells may be filled with the universe of
the lattice cell itself. This syntax indicates to MCNP that the cell should be
filled with the material of the lattice cell. Using 0
as a universe number
for the subcells is supported and results in no subcell being generated.
Here is how the example above is converted and rendered in TRIPOLI-4:
Current limitations
Here is a list of some things that t4_geom_convert
cannot currently do, but
may be able to do in the future (in roughly decreasing order of likelihood):
-
Convert SQ surfaces (tracked in issue #11)
-
Import the title of the MCNP input file (tracked in issue #5)
-
Handle affine transformations with
m=-1
(the last parameter of the affine transformation) (tracked in issue #12) -
Optimize fills with negative universes (do not intersect with the enclosing cell) (tracked in issue #13)
-
Warn about isotopes that are missing from the TRIPOLI-4 dictionary (currently you need to edit the converted file by hand and remove the occurrences of the missing isotopes)
-
Convert MCNP macrobodies
-
Convert cell temperatures
-
In the fully-specified lattice syntax, handle the case where the subcell universe is equal to the universe of the lattice cell.
-
Convert hexagonal lattices
-
Import comments describing the MCNP cells/surfaces (tracked in issue #9)
-
Provide a way to specify lattice fill ranges per enclosing cell(s) (this needs to be specified in such a way that it works with nested lattices, too)
-
Deduplicate repeated surface definitions, i.e. remove duplicate surface definitions in favour of one of the replicas (this is especially an issue for lattices, that tend to generate lots of identical surfaces)Fixed in issue #19
-
Deduplicate repeated cell definitions (this is a bit harder than deduplicating surfaces)
-
Produce a TRIPOLI-4 connectivity map for as many cells as possible (mostly lattices)
-
Recognize and automatically suppress empty cells (they may be generated by lattice development or fill development)
- Use a linear programming solver for cells bounded by planes?
- Use a SAT solver in the general case?
-
Convert (some) MCNP source definitions
-
Convert (some) MCNP tally definitions
A couple of limitations are due to MIP/TatSu:
-
MIP does not support TatSu>4.3.0 (something breaks, but I'm not sure what exactly yet)
-
Input files cannot contain unusual or non-ASCII characters such as&
oré
; you need to remove these characters from your input file before attempting the conversionFixed upstream
-
Spaces are not permitted in a cell definition between a complement operator#
and its argument:good:#42
good:#(123 -124)
bad:# 42
bad:# (123 -124)
Fixed in issue #10
Your help is welcome! Feel free to open an issue if you would like to implement a new feature or contribute to the project in any way.
The full changelog is here.
Reporting bugs
Please report any bug/feature request on the GitHub issues page.
Licence and acknowledgments
The development of t4_geom_convert
was partially financed by the EUROfusion
consortium. t4_geom_convert
is released under the terms of the GNU Public
Licence, version 3.
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